Where to buy in Japan?

We're on a trip to Japan on May (yes... maybe I post this too soon but I'm oh-so-excited about this!! yay!) we're probably going to tokyo and kyoto and somewhere else we are still discussing.

I'd love to know if I can buy bento gear anywhere (i mean combinis) or if there are specific places to buy, like malls or places like that.
By bento gear i mean things different than the ones appearing on on-line shops or e-bay. I'm very sick of anime-decorated or childish bentos, I'd love to buy cute yet "adult" boxes.